Pressure-retaining mechanism for fluid-pressure brakes.



No. 772,167. PATENTED OCT. 11, 1904. F. MERTSHEIMER.

PRESSURE RETAINING MECHANISM FOR FLUID PRESSURE BRAKES.

APPLICATION FILED JAN. 22. 1994. no MODEL. s SHEETS-SHEET 1.

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RMERTSHEIMER.

PRESSURE RETAINING MECHANISM FOR FLUID PRESSURE BRAKES.

' APPLICATION FILED JAN; 22. 1904. N0 MODEL. SSEEETS-SHEETQ.

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I PATENTED OCT. 11,"1.904. F. MERTSHEIMER.

PRESSURE RETAINING MECHANISM FOR FLUID PRESSUREBRAKES.

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Z592 v f APPLIGATION FILED IAN. 22. 1904.

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UNITED STATES Patented October 11, 1904.

PATENT OFFICE.

FREDERICK MERTSHEIMER, OF DENVER, COLORADO.

PRESSURE-RETAINING MECHANISM FOR FLUID-PRESSURE BRAKES.

SPECIFICATION forming part'of Letters Patent No. 772,167, dated October 11, 1904.

Applica ioufilcd Jannary2 2,1 9(l4. Serial No. 190,184. (NomodelJ sure of air suflicient to render the brakes ef.

fective and prevent any acceleration of speed of the car or train after the triple valve has moved to position for permitting air to escape from the brake-cylinder and while the auxiliary reservoir is being rechargedfroin the train-pipe. v

The pressure-retaining valve is usually secured to one end of the car and connected to the exhaust-port of the triple valve by means of a small pipe, the arrangement being such' that by turning a cock on the retaining-valve to difierent positions the air from the brakecylinder will be exhausted either directly to the atmosphere or through the retaining-valve held to its seat by a certain predetermined weight which must be overcome before the air escapes and which closes as soon asthe pressure of air falls below that of the weight holding the valve closed, thus retaining within the brake-cylinder a pressure equal to the weight of the valve.

My pressure-retaining device embodies two weighted valves, one valve being preferably held closed by a weight sufiicient to maintain a minimum pressure in the brake cylinder, while the other valve carries a weight which ofiers additional resistance to the exhaust from the brake-cylinder and which, added to that of thefirst-mentioned valve, will be sulficient to retain a maximum pressure in the brakecylinder. If desired, more than two weighted valves may be used, their combined weight equaling the maximum pressure to'be retained.

In the accompanying drawings, Figure 1 lightest cars.

represents aside elevation of one end of a freight-car with my invention secured thereto and so much of the brake mechanism as will illustrate its application. end view of the same. Fig. 3 is afr'ont view of my pressure-retaining valve on a larger scale. Fig. 4 is a vertical section on the line A A. Figs. 5, 6, and 7 are sectional views on the line B B of Fig. 4:, showing the parts arranged for three separate operations.

Similar numerals indicate the same parts in the several figures.

Below the body of the car 1 is secured the usual air-brake mechanism, of which the cylinder 2, auxiliary reservoir 8, and triple valve 4, connected .to the train-pipe 5, alone are shown.' From the exhaust-port of the triple valve 4 a small pipe 6 extends longitudinally beneath the car to one end thereof, where it "is carried upward to a point near the top of the car and fitted with a pressure-retaining valve 7, acting to retain within the brake-cylinderwhen the brake mechanism is released a certain pressure, usually about fifteen pounds per square inch, to hold the brakes set and prevent the speed of a train from accelerating,

Fig. 2 is an as when descending grades, thereby permit ting the auxiliary reservoirs to be recharged.

It is the common practice to use a pressureretaining valve which will close when the pressure in the brake-cylinder falls to the same predetermined point, so that however steep the grade of the railroad or great the weight of the car no increase of pressure can be maintained within the brake-cylinder for holding the brakes with greater power than when on theslightest descent and with the My invention is designed to obviate this difiiculty by the improved pressure-retaining valve illustrated more clearly in Figs. 3 to 7, both inclusive. As there shown, 8 indicates a casting provided with a plug cock 9, passing transversely therethrough near its center, in which is formed a right-angled passage 10. A handle 11, fitted to the cock at one end, is used for turning it through an arc of one hundred and eighty degrees, greater movement being prevented by means of stops on the outside of the casting 8, against which the handle 11 strikes. Within the top of the casting 8 are formed two circular depressions 12 and 13in close proximity to each other, into each of which is screwed or otherwise fastened a cylindrical casing 1 L. A passage 15, which extends from the under side of the casting 8 to the plug-cock 9, is

threaded at its lower end to receive the ex,

haust-pipe 6 from the triple valve. Ports 16 and 17 pass downwardly from the depressions 12 and 13, the former port connecting with the plug-cock'9 at a point ninety degrees from the passage 15, while the latter port 17 passes around the plug-cock and connects with the passage 15 below said cock. Weighted valves 18 19 close the respective ports 16 and 17, as shown. The depression 13 is connected by a port 20 to the port 16 below the weighted valve 18, while the depression 12 is open to the atmosphere through the port 21. A port 22 extends to the atmosphere from the side of the plug-cock 9 opposite the port 16. The weights 23 24:, holding the valves 18 19 closed, are, as shown in the drawings, equal. This, however, is not necessary, as the weight 24 may be greater or lesser than the weight 23.

In the operation of my invention when all the air is to be exhausted from the brake-cylinder the plug-cock 9 is turned as in Fig. &, the angular passage 10 in the plug connecting the passage 15 with the port 22 open to the atmosphere. If the minimum pressure is to be retained in the brake-cylinder, the cock 9 is turned by its handle to the left. This changes the angular passage 10 to the position shown in Fig. 6. The open port 22 is now closed and communication established between the passage 15 and the port 16. The port 16 being closed by the weighted valve 18, it must be raised before any compressed air can escape from the brake-cylinder to the atmosphere through the small port 21. The weight 23 is preferably such as will close only when the pressure is reduced to its minimum say fifteen pounds per square inch. Should a train be descending a steep grade with loaded cars, it is very desirable to have a greater retaining-pressure in the brake-cylinders than would be the case were the cars running light. This increased pressure I obtain by means of a second weighted valve 19. On turning the plug-cock 9 to the position illustrated in Fig. 7 ports 16 and 22 are closed to the passage 15. The compressed air therefore in order to escape must pass up the port 17 and, raising the weighted valve 19, flows through the port 20 to port 16. The air then opens the weighted valve 18 and finally escapes through the port 21 to the atmosphere. The pressure of air retained in the brake-cylinder is equal to the sum of the resistance offered by the two valves. For instance, if the weighted valves 18 and 19 have each a resistance of fifteen pounds the pressure retained is equal to thirty pounds. Should a retaining pressure be desired greater or lesser than thirty pounds,

but more than fifteen pounds, the size of the weight 2 1 would be enlarged or reduced to such an extent that its resistance, plus the resistance of the weight 23, is equal to the pressure required. The principle on which my device operates is this: Assume the resistance of the weighted valve 18 to be fifteen pounds, while that of the valve 19 is ten pounds. Vith a pressure of ten pounds in the port 17 the valve 19 will be in equilibrium. A pressure of fifteen pounds in the port 17 will raise the valve 19 and bear against the valve 18 with a force of five pounds,the difference between the acting pressure and that required to raise the valve 19. There will also be a pressure of five pounds reacting on the top of the weight 24. If the pressure is increased to twenty pounds, there will be ten pounds acting on the valve 18 and the weight 24:, while a pressure of twenty-five pounds will raise the valve 18 and press on the weight with a force offifteen pounds, which added to its own resistance of ten pounds gives the valve 19 a resistance of twenty-five pounds, for which reason it is called the high-pressure-retaining valve. It will thus be seen that by combining two or more weighted valves so arranged that they discharge from one to another in succession before opening into the atmosphere any desired retarding pressure may be obtained.

I have found from experiment that when two or more weighted valves are used, as above described, to retain a relatively high pressure in the brake-cylinder a longer period of time is required to exhaust the air down to the retaining pressure than where a single valve is used having the same resistance as the combined valves, so that the engineer will have ample time to get up pressure sufficient to recharge the auxiliary reservoirs. WVhile the weighted valve 19 is identical in construction with the valve 18, except as to the direct communication of the latter with the atmosphere and while for convenience of description I have referred to this valve 19 as a high-pressure-retaining valve, it becomes effective for this purpose only in the respect that it cooperates with the other valve in offering to the exhaust from the brake-cylinder an additional predetermined resistance to that which the exhaust encounters in passing through the valve 18 to the atmosphere. The essence of the invention resides, therefore, in combining with a pressure-retaining device adapted to be placed in communication with the exhaust from the brake-cylinder and formed to retain a predetermined pressure in brake-cylinder means for offering to the exhaust before it reaches said pressure-retaining devicea predetermined resistance, the result being that the pressure necessary to find its exit to the atmosphere must equal the combined resistance offered by the pressure-retaining device and that offered to the exhaust before it reaches said device. It is obvious, therefore, that the formof the valve 19 may be variously modified and, provided'its action is as above described, it will fall'within the limits of my invention.

Having thus described my invention, what I claim is- 1. In afluid-pressure brake system,the combinati on with a brake-cylinder and an exhaustduct leading therefrom, of a pressure-retaining mechanism adapted to retain different predetermined pressures in the brake-cylinder, said mechanism comprising a valve-casing provided with an entrance-port communicating with the exhaust-duct, and having a Weighted gravitating valve therein controlling said entrance-port, and a second valve-casing provided with an entrance-port communicating both with the first casing and with the exhaustduct, and having a weighted gravitating valve controlling said entrance-port, said valve-casing being open to the atmosphere, a port 22 open to the atmosphere and adapted to be placed in communication with the exhaustduct at a point beyond the communication of the first valve-casing with said duct, and a controlling device adapted to open or close communication of port 22 with the exhaustduct, and to open or close communication of said exhaust-duct with the entrance-portto the second valve-casing.

2. In a fluid-pressure brake system,the combination with the brake-cylinder, of a pressure-retaining valve comprising a casing open to the atmosphere with a port entering the same, and a movable valve controlling said port, an exhaust-passage leading from the brake-cylinder and connecting with said port, a second valve-casing, a port entering the same and having a constant connection with the exhaust-passage, a movable valve in said casing controlling its port, a communicating passage between the second casing and the exhaust-passage, and means for shutting off the direct connection of the exhaust with the first casing; whereby the exhaust may be caused to pass through the second valve-casing before entering thefirst, and be subjected in its passage to the reducing action of the valve of the second casing.

3. In a fluid-pressure brake system,the combination of a brake-cylinder, a low-pressureretainingvalve opening to the atmosphere, a high-pressure-retaining valve having communication only with'the under side of the lowpressure-retaining valve, each of said valves being adapted to be placed in communication with the exhaust .from said brake-cylinder, and means for exhausting the pressure directly through the low pressure retaining valve only, or indirectly by first passing through the high-pressure-retaining valve.

4:. In a fluid-pressure brake system,the combination of a brake-cylinder, a low-pressureretaining valve opening to the atmosphere, a

high-pressure-retaining valve having communication only wlth the under side of the lowpressureeretalning valve, each of said valves being adapted to be placed in communicationwith the exhaust from said brake-cylinder, a port opening to the atmosphere, and a plugcock having a port therethrough by means of which the cylinder-pressure may be exhausted into the air through the low-pressure-retaining valve, or through the two valves in succession.

In testimony whereof I hereunto set my hand, this 14th day of January, 1904:, in the presence of two attesting witnesses.

FREDERICK MERTSHEIMER.

Witnesses:

W. B. DUNLEVY, RoB'r. L. LANGTIM. 

